1. Field of the Invention
The present invention pertains to repair of printed circuit board assemblies utilizing surface mounted components and more particularly to a tool useful in the process of repairing or replacing surface mounted electronic components attached to printed circuit boards.
2. Background Art
The process of attaching or positioning surface mounted components to printed circuit boards requires a number of steps including the precision application of a solder paste to the printed circuit board pads used to mount the electronic surface mounted components. Also required is the use of hand placement or high speed automated placement of surface mounted components into the solder paste previously applied. This step is then followed by melting the solder paste via vapor phase reflow soldering, infra red reflow soldering, or similar equivalent techniques. Finally, the soldering process is followed by the cleaning, inspection and repair of the printed circuit board assembly.
Normally, prior to the reflow soldering step in the process, inspection, followed by repair and/or repositioning of the surface mounted component relative to the solder paste and pad may be required to assure a high quality, highly reliable assembly. This presolder inspection and repair process is usually accomplished utilizing manual methods. Manual methods usually include manual inspection followed by manual repositioning which requires the relying on the dexterity and accuracy of the inspector to perfect the manual reposition of the component prior to reflow soldering.
Most recently, the use of automatic inspection techniques, such as automated optical inspection, have been developed for qualifying both the solder deposition characteristics as well as the accuracy of the component placement, whether it is done manually or by automatic process. However, in either case of inspection, whether it be manual or automatic, the task of correcting defective component positioning has remained an exclusively manual task. The usual techniques required for repositioning components typically employ the use of "tweezers" or probes to push or turn the component to achieve the proper relationship, i.e., orientation, of the surface mounted component leads to the printed circuit board mounting pads. As can be expected, this process is a highly subjective one, relying on the operator perception and dexterity exclusively. It has also been found that in addition the act of pushing or turning while in contact with the solder paste can cause a so-called "snowplow" effect, forcing the solder paste to bridge to an adjacent mounting pad leading to the possibility of electrical short circuits. In addition, since the solder paste interface between the printed circuit board and the component has a certain height or thickness parameter to offset irregularities in component lead position or co-planarity and to provide sufficient solder volume to ensure a good solder joint, any disruption of this paste jeopardizes this particular requirement.